The present project proposes to study the intracellular changes that occur in the distribution of aminoacyl-tRNA synthetases during development of the brine shrimp, Artemia Salina. The transformation of ametabolic cysts into metabolically active nauplii occurs in the absence of significant DNA/RNA synthesis or cell division. Thus it represents a unique system for studying developmental changes in the machinery for protein synthesis. Accumulating evidence from numerous biochemical studies supports a model of protein synthesis in which many or most of the enzymes and coenzymes necessary for protein elongation are part of a large molecular weight complex necessary for efficient in vivo protein synthesis. A time course study of changes in the intracellular distribution of synthetase could reveal obligatory requirements for efficient protein synthesis and could provide insight into possible regulatory mechanisms that would serve to modulate overall protein synthesis in eukaryotic cells. The fact that synthetase complexes are unique to eukaryotic provides yet another difference that could be successfully exploited by an antibiotic.